This invention is concerned with improvements in the fabrication of transparent laminated polarizing glasses which are particularly useful in eyeglass lenses.
U.S. application Ser. No. 734,848, filed May 16, 1985 by Serge P. P. Goepfert, and Gildas J. M. Guillevic under the title LAMINATED TRANSPARENT POLARIZING GLASSES AND METHOD OF MAKING, describes transparent laminated polarizing glass articles comprising:
(a) a support of an inorganic or organic glass;
(b) a coating exhibiting polarizing properties applied to one of the surfaces of the support; and
(c) an optically transparent composite film in a single piece consisting on one side, of a ply of thermoplastic polyurethane with adhesive properties and, on the other side, of a ply of thermosetting polyurethane with anti-lacerative and self-regenerating properties, the thermoplastic polyurethane adhering to the coating with polarizing properties.
The support can advantageously be a glass with photochromic properties.
The polarizing coating can be formed of a mixture of three organic colorants corresponding to the three primary colors blue, red, and yellow and exhibiting a nematic state, the aforesaid polarizing coating being of reduced water solubility as a result of an ion exchange treatment through an aqueous acidic solution of inorganic salts.
In the composite film the thermoplastic polyurethane is formed by means of an aliphatic diisocyanate and a diol of an aliphatic diacid polyester or a diol of a polyglycol ether, each of the said diols having a molecular weight of 500-4000; and the thermosetting polyurethane is the product of (a) a polyglycol ether resulting from the combination of an epoxy-1,2-propane with 2,2-bis(hydroxymethyl)1-butanol and containing 10.5-12% by weight of free hydroxyls, and (b) a biuret of 1,6-hexamethylene diisocyanate containing 21-22% by weight of isocyanate groups, the weight of said biuret comprising between 0.9-1.1 times the weight of said polyglycol ether, the thickness of the thermoplastic polyurethane being of 0.01-0.8 mm and the thickness of the thermosetting polyurethane being of 0.2-0.8 mm.
If desired, the composite film can be subjected to a coloration treatment.
A process for the fabrication of transparent laminated polarizing glass articles is also described in the above patent application.
In U.S. application Ser. No. 717,829, filed Mar. 29, 1985 in the names of Serge P. P. Goepfert, Serge A. M. Renault, and Francoise M. M. Roger under the title of IMPROVEMENTS IN THE MANUFACTURE OF LAMINATED TRANSPARENT, POLARIZING GLASSES, is described an improved process for fabricating transparent laminated polarizing glass articles comprising the following steps:
(a) forming parallel microgrooves in a surface of the inorganic or organic glass support with the help of a slightly abrasive brushing of the said support prior to applying the polarizing coating thereon;
(b) carefully washing and drying this surface of the support prior to applying the polarizing coating thereon;
(c) depositing a mixture of three organic colorants corresponding to the three primary colors and exhibiting a nematic state on the washed and dried surface of the support;
(d) treating the polarizing coating to reduce the water solubility of the coating by immersing it into an aqueous solution of inorganic salts having an acid pH; and
(e) applying a composite polyurethane film by first subjecting it to moderate conditions of temperature and pressure in order to assure a gradual spreading out free from wrinkles and an adherence of the film to the polarizing coating; then to elevated conditions of temperature and pressure in order to strengthen the mechanical bond between the film and the coating and to achieve reticulation of the composite film, this process comprising the supplementary step consisting of placing the product resulting from Step (d) above in contact with an aqueous solution free of organic co-solvent prepared from at least one compound chosen from among gamma-aminopropyltrimethoxysilane and gamma-aminopropyltriethoxysilane, the silane representing 0.1-10% by volume of the solution and the aqueous solution having a pH in the range of 10-11.2.
The duration of the silane treatment can be from 2-60 minutes at a temperature not exceeding 30.degree. C. This treatment is followed by rinsing in water and a heat treatment between 80.degree.-140.degree. C. for a duration of 15-60 minutes, for example.
The object of the silane treatment is to strengthen the resistance of the bond between the polarizing coating and the glass support, on the one hand, and between the polarizing coating and the composite polyurethane film, on the other hand, thereby permitting better conditions of spreading of the film and also dispensing with the need to apply a layer of resin on the edge of the laminated glass, as instructed in the above patent application.
Notwithstanding the strengthening of the bonding forces, the laminated glass prepared in accordance with U.S. application Ser. No. 717,829 still exhibited certain deficiencies of bond. Delamination around the periphery of the glass composite sometimes becomes apparent in wearing and because of aging:
in particularly harsh atmospheric conditions, such as high relative humidity coupled with a high temperature (tropical and equatorial climate); and
under the effect of the condensation of perspiration which varies according to the individual.